Fattening mechanism revealed

Part of the chemical machinery behind the obesity epidemic has been exposed.

A team of Yale researchers discovered one mechanism responsible for fat cells’ efficient storage and use of food energy. In its Oct. 5 paper in the journal “Cell Biology,” the team identified the process by which the chemical choline allows fat cells to expand when a person overeats.

Tobias Walther, associate professor of cell biology, led the 12-person research team as they set out to investigate the mechanics behind lipid droplets — small bodies of oil used by cells to store energy.

“Lipid droplets can expand over several orders of magnitude and contract again very quickly,” Walther said. “So we were trying to understand how that happens.”

The experiment revealed that phosphatidylcholine, a lipid with a choline base, is required for cells’ fat droplets to grow, according to the paper. Without a supply of phosphatidylcholine, lipid droplet membranes lose strength, causing droplets to fuse together like oil drops do in water.

Walther said the new study is important partly because it identifies the formerly unknown chemical processes behind fat droplets’ expansion and contraction cycles. When the cycle falters and droplets fuse, fat begins to accumulate and the cell mechanisms responsible for energy mobilization may fail, raising the risk of obesity and related health problems.

Robert Farese, senior investigator at Gladstone Institute of Cardiovascular Disease that participated in the study, said this type of experiment, which investigates the mechanisms of organic chemical processes, became popular after the completion of the Human Genome Project — an effort to catalogue all 23,000 protein-coding genes in the human genetic code.

“From the Human Genome Project, we got a parts list,” Farese said. “Now, studies like this are aimed at figuring out how those parts work together to make the human.”

The study could contribute to the development of better obesity and fatty liver disease treatments, and researchers may be able to use the proven relationship between phosphatidylcholine and obesity in order to determine patients’ risk for obesity and other metabolic problems, such as diabetes, Farese said.

“Obesity currently affects more than 93 million Americans, and 1 out of every 3 children,” said James Zervios, director of communications for Obesity Action Coalition. “And these numbers are predicted to rise.”

Further research is required before scientists can make significant progress toward improved preventative or therapeutic techniques, Farese said. In the meantime, the researchers plan to study fat cells in greater depth to discover how they form and how their internal protein machinery functions, he added.

Choline is a chemical compound found in egg yolks and soy beans. Increasing choline intake will not affect cells’ fat storage because most people already consume enough choline, according to the researchers.